High-frequency coupling device



June 1, 1937- c. c. NEIGHBoRs E-r AL 082,590

HIGH FREQUENCY COUPLING DEVICE Filed Oct. 23, 1934 IN VENTOR.

MQW

ATTORNEY.

Patented June 1,. 1937 ,im oFFlcE 2,082,590 HIGH-FREQUENCY COUPLIN G DEVICE Charles C. Neighbors and Wilfred H. James, Chicago, lll., assignors to Johnson Laboratories,

ihicagn, Eli., a, corporation of Illinois Application October 23,

8 Claims.

therrrn'onic relay, a resonant system consisting of two inductors and their tuning capacitors, the l inductors being arranged either in magnetic relation or else capacitively coupled to each other. The capacitors are normally of a type having very low losses, and include means for a small adjustment of the capacitance.` `The emciency of the complete design depends to a very large extent upon the inductors.

An object of this' invention is to provide novel types of coupling means for use in such amplifying systems, which, because of their design, will4 materially increase thel eiliciency of the system. Additionally, it is the object of this invention to provide designs for the resonant circuits of such amplifying systems which will be more compact, and which can be easily adjusted to the desired coupling.

Further objects of the invention are attained by the employment ci cylindrical and preferably hollow magnetic cores for the inductors in order that, when they are adjusted relatively to each other, values of coupling ranging from negligible to somewhat greater than optimum may be readily secured. The hollow cores also provide a more economical form than solid cores, and incidentally aiord means for their ideal mounting.

A still further object of the invention is attained by so mounting the inductors that their axes are at right angles to the longest dimension of the shield can which is used in conjunction with such devices. This shield is usually neces- 40 'sary to prevent interaction between vadjacent components of the equipment and the inductors of the device, and incidentally provides convenient mounting means and mechanical protection for the device. It has been found that the abovedescribed positioning of the inductors gives an advantageous reduction in losses when the device is housed in a compact shield.

Additional objects of the invention are attained by provision for convenient adjustment of the degree of coupling between the inductors from without the shield, and for establishing the spacing of the leads to the inductors in order to prevent undesired variations in the stray capacitances of the device, as for instance might occur were one of the leads to shift relatively to the shield.

Circuits of the class here contemplated normaliy occur in pairs, one resonant circuit being connected to the output terminals of a rst thero0 minnie relay, and another circuit being connect- 1934, Serial N0. 749,661 (Cl. 178-44) ed to the input terminals of a second thermionic relay. In order to develop a maximum voltage 'n the second resonant circuit due to current in the first, the inductors are normally coupled lnductively. The inductor in the circuit connected to the output terminals of the first thermlonic relay is usually called the primary, and the inductor in the circuit connected to the input terminals of the second thermionic relay is usuallyoperate strictly as an amplier. These variations, however, are not material with respect to the application'and scope of the present invention.

In present-day designs, coupling devices of the class here under consideration normally do not employ magnetic cores. Across the lirst inductor, and also across the second inductor, there is connected a capacitor whose capacitance is adjustable over a limited range. By suitably designing the primary and secondary inductors and by adjustment of the associated capacitors, each of the circuits may be tuned to be resonant at the desired frequency. In order to develop a maximum voltage across the second inductor due to the current in the iirst inductor, it is essential that the inductive coupling between the two inductors shall be closely of the optimum value. In present designs, it is customary to establish the degree of coupling in the design of the device, so that when the inductors are assembled, the proper coupling will exist.

Because of the losses which normally exist in air-core inductors of the type now commonly used, it is not essential to provide means for adjusting the coupling between the primary and secondary inductors after the unit is assembled. It is usually suiicient to determine experimentally what physical relation between the two inductors will give approximately the correct coupling and then to mechanically design the device so as to produce this relation.

In the designs herein described, the losses in thev inductors themselves are greatly decreased, and it therefore becomes desirable to provide means for accurately adjusting each unit to the desired coupling between primary and'secondary. The present invention, therefore, includes designs for inductors having greatly increased eiliciency, and arrangements whereby two such inductors may be inductively related in a coupling device with means for producing an accurate adjustment of the inductive coupling. The inductive coupling may be arranged to either add to or oppose the inherent capacitive coupling.

The increased eiciency of the inductors themselves is secured by introducing a magnetic core. These cores are preferably of a. type made by compressing individually insulated magnetic particles of very small size. The size of the particles which will be most advantageous for use in any particular design will depend largely upon the frequency for which the system is being designed. In general, the higher the frequency, the smaller the particles will be. The insulation of the individual particles must be sufhciently complete to produce a very high electrical resistivity in the compressed comminuted core, which will then have very low electrical losses.

In cores of this preferred type, itis readily possible to secure effective permeability of the or der of from 2 to 4. This greatly decreases the size of the winding itself, because less turns are required for any desired value of inductance. This materially decreases the resistance of the winding. Since the losses in air-core inductors of present designs are the chief source of inefficiency in high-frequency coupling devices, a reduction in the size of the winding will produce a corresponding decrease in the losses of the system, provided that the losses introduced by the introduction of the magnetic core are sufficiently small. Cores of the type which we have described possess this property of extremely low losses, so that our iron-core inductors are very much more efficient than the equivalent air-core inductors.

Because of the higher efficiency of the ironcore inductors, it is possible to obtain greater secondary voltage with less coupling than is permissible with air-core inductors. This results in an increase in the electrical efficiency of the device. In a high-frequency amplifier, for example, it is possible to get substantially twice the amplification while maintaining the selectivity the same as it would be with air-core inductors, or, if desired, it is possible to obtain approximately twice the selectivity while maintaining the same amplification. Similarly, a fifty per cent. increase in both amplification and selectivity can be secured.

This invention will be better understood by reference to the accompanying drawing, which is illustrative of practicable mechanical embodiments of the invention. It will be understood that numerous mechanical arrangements other than those shown may be employed to provide means for mechanical adjustments to vary the inductive coupling between the primary and secondary inductors, all within the scope of the present invention.

Referring to the drawing, Figure 1 is an elevation, partly in section, of a high-frequency coupling device employing magnetic cores;

Figure 2 is an elevation, in section, taken at line 2--2 of Figure 1;

Figure 3 is an elevation, partly in section, of a modified form of high-frequency coupling device, and

Figure 4 is an elevation, in section, taken at line 4--4 of Figure 3.

Referring to Figures 1 and 2, the device here illustrated includes an insulating base I, preferably of a ceramic material. Secured to the base I are capacitors 2 and 3, which are so designed that their capacitances are adjustable over a limited range. The capacitance of capacitor 2 is altered by means of nut 4, and the capacitance of capacitor 3 is adjusted by means of screw 5, located inside of nut 4.

Frame 6 is preferably cast or molded in one piece of an insulating material such as bakelite, to avoid the cost of assembling operations which would be necessary if it included, as it might, a plurality of elements. Threaded inserts 1 are molded into the feet of frame 6, and, in conjunction with sleeves 8 and nuts 9, secure the frame 6 to the base I. Inserts I also pass through holes in the top of shield I0, thereby serving to maintain the base I in a definite position relative to shield I0. A hole in the top of shield I I) gives access to adjustments 4 and 5 of capacitors 2 and 3.

Coil II, which is preferably of the universalwound type1 is cemented or otherwise suitably secured to its cylindrical magnetic core I2, which in turn is mounted on frame 6 by means of insulating rod I3. As shown, the axis of the inductor II--I2 is perpendicular to the longitudinal axis of shield I0. Coil I4, of the same construction and usually of the same size as coil II, is likewise mounted on its core I5, which in turn is secured to the insulating rod I6. A threaded insert I'I is molded into the end of rod I6, and passes through a slot I8 in frame 6. The nut I9 serves to secure inductor I4--I5 in a desired position relative to inductor II-I2, and access is had to nut I9 through a suitable opening 20 in shield I0.

The slot IB in the frame 6 is of length sufficient to provide the necessary range of coupling variation required by the design.

The leads 2I to the device are secured in slots 22 in frame B by means of tape bands 23 or in any other suitable manner. The whole device is mounted upon the chassis of the equipment with which it is to be used by means of threaded studs 24 suitably secured to the shield I0.

In quantity production of devices of the type shown in Figure 1, it will usually be preferable to design the insulating frame 6 with the slot IB to permit coupling adjustment. After a considerable number of units have been manufactured, the exact position for the movable inductor to give the proper degree of coupling for the par ticular design will be known, and a jig may be made so that the inductors may be accurately positioned in the slot without resort to any electrical method of observing the performance of each device.

Inductor I4-I5, therefore, may be fixed in a predetermined desired position relative to inductor II--I2, instead of being adjustable, with out departing from the scope of the present in vention. This makes possible a slight reduction in the cost of manufacture of the device without sacrificing any important feature of the invention.

The device shown in Figures 3 and 4 employs a different method of mounting the inductors and also has an alternative arrangement for varying the coupling between them. An insulating base I, preferably of a ceramic material, has mounted on it adjustable capacitors 25 and 26, which are adjustable by screws 21 operating in countersunk nuts 2B. Insulating brackets 29 supporting inductors II-I2 and I4-I5 are secured to base I by means of bolts 30 and nuts 3I. Bolts 30 together with nuts 3Ia also secure base I to the shield can I0, which in this embodiment is of rectangular cross section.

The leads 2I to the device pass through grooves 22 in base I, and connecting holes 22a convey the leads through the base to the terminals of the capacitors. Base I also supports shaft 32, which has a slot for a screwdriver at its outer end, and to the inner end of which is attached metallic vane 33, preferably made of copper or aluminum.

accanto shield, and therefore to ground, 31 prevents the shaft 32 from rotating suiilciently to sever lead 36.

Shield can I0 is provided with holes to receive screws 2l and shaft 32, and with suitably attached threaded pieces 24 for securing the whole device to the chassis of the equipment with which it is to be used. Thus adjustment o! the capacitances of capacitors 25 and 26, and of the position of vane 33, is readily made from without the shield even after assembly of the device on the chassis ofv the equipment.

The inductive coupling between the inductors may be varied over a substantial range by rotating the metallic vane 33. The presence of an ungrounded vane will appreciably increase the capacitive coupling between the inductors. If the vane is grounded by means of lead 36. capacitive coupling between the inductors will be considerably decreased.

In either embodiment shown, the lnductive coupling adds to or opposes present invention.

It will be noted that the methods used in the present invention for adjusting the coupling between the inductors of the device are such that the adjustment may be readily changed when desired.

Various methods for making the vane 33 remain xed in a desired position may be em ployed, as for instance a spring washer under collar 35. In other cases, rotation of the vane is the degree of selectivity of the coupling device, as for instance to permit wide-band or highly selective performance from the same device at the option of the operator. By mechanically ganging the vanes of several units, a substantial range in selectivity may be readily obtained.

Having thus described our invention, what We claim is:

1. A high-frequency coupling device including two resonant circuits optimum coupling between said circuits.

2. A high-frequency coupling device including two resonant circuits each having an inductor, said inductors each having a winding and a comminuted magnetic core, a conductive shield surother as to secure pling between said 3. A high-frequency coupling device including two resonant circuits each having an inductor, said inductors each having a winding and a comminuted magnetic core, a conductive shield sursaid inductors from said shield and for so spacother as to secure substantially optimum coupling between said circuits, said frame being mounted upon the closed end of said shield.

4. A high-frequency coupling device including at least two resonant circuits each having an inductor, tubular magnetic cores for each of said be mounted on one side of said shield whereby desired coupling between said inductors is achieved.

5. A high-frequency coupling device including at least two resonant circuits each having an parallel, and a conductive rotatable vane positioned between said inductors for varying the inductive coupling therebetween, whereby desired coupling between said inductors is achieved.

6. A high-frequency coupling device including two resonant circuits each having an inductor, said inductors each having a winding and a comangles to the axis of said shield to reduce the coupling between said inductors, and means pling between said circuits.

7. A high-frequency coupling device including at least two resonant circuits each having an inductor, means for supporting said inductors with their axes parallel but in spaced relation, a conductive shield surrounding said inductors, a conachieved.

8. A high-frequency coupling device including two resonant circuits each having an inductor, said inductors each havinga winding and a comductors may be adjusted to secure substantially optimum coupling between said circuits.

CHARLES C. NEIGHBORS. WILFRED H. JAMES. 

